EP 1 347 154 A2 discloses a rotary drive designed for an adjustment shaft of a variable valve drive. A first rotatory, hydraulic drive is connected to a second rotatory, hydraulic drive in such a way as to allow rough and fine adjustment of the exact eccentric position within a valve drive chain. In other words, the angle of rotation position to be set is facilitated by a two-stage system.
U.S. Pat. No. 2,911,956 describes a plate-shaped positioner by means of which a pivoting movement of a first plate influences the pivoting range of a second plate and so on.
WO 01/12996 A1 shows in FIG. 5a a two-stator shaft adjustment system in which the rotor is restricted in its pivoting range by the rotation of a first and second stator.
U.S. Pat. No. 5,233,948 discloses what advantages can be obtained if the cams of superimposed cam shafts are adjustable relative to one another. It is possible to infer from this disclosure the desire to create valve drives which are configured in such a way that they can individually control results of a plurality of gas exchange valves of a combustion chamber. Although this reference discloses the theoretical advantages, there are no proposals for a specific implementation. The basic principles which are theoretically disclosed in this reference are deemed to be incorporated herein by reference.
Approaches for carrying out the teaching of U.S. Pat. No. 5,233,948 are known from FIGS. 4A to 4C of U.S. Pat. No. 5,235,939 which illustrates a coaxial double cam shaft with at least two sets of cams which are angularly offset relative to one another and the cams of which are fastened to the respective carrying cam shaft by fastening pins and fastening springs. A similar arrangement is known from WO 2005/040562 A1. According to the description, the cam position is to be adjusted using hydraulic linear cylinders. A similar design is known from FIG. 1 of DE 43 32 868 A1, which is likewise intended to adjust, by way of a linear movement, the cam position of an inlet cam relative to an outlet cam. The account in EP 0 397 540 A1 also shows a linear-adjustable cam shaft arrangement. FIGS. 5 and 6 of U.S. Pat. No. 4,332,222 disclose a contoured feed pin which influences via its surface the angular distance between two cams and thus the relative position of the connected cam shafts. According to DE 36 24 827 A1, two meshing hollow shaft cam shafts can be adjusted relative to each other in their angular position via a planetary gear with longitudinal holes. However, in order to comply with current exhaust gas values in high-compression combustion engines, the outer shaft must also be adjustable relative to the driving shaft, in particular the crank shaft. DE 199 14 909 A1 discloses further grounds for creating a nested cam contour. The cam contour of the main cam of a cam shaft can be extended by an auxiliary cam in order to activate the associated gas exchange valve a second time, in a time-offset manner relative to the main event, and thus to allow reloading of, or a further outflow from, the cylinder. Finally, reference should also be made to the two documents JP 11 17 31 20 and WO 1992/012 333, which may also be relevant as background information.
In summary, it is clear that it has for years been a recurring consideration how events which are to be offset from one another over time can be made adjustable in their phase positions in the gas exchange valve drive.
DE 10 2005 014 680 A1 shows in certain graphical illustrations a double cam shaft which is equipped with a connected, grooved oil transfer piece, thus allowing the hydraulic oil to be forwarded to a hydraulic adjuster (not shown).
A cam shaft adjuster for the relative rotation of a hollow cam shaft and a second chain wheel arranged parallel to the first chain wheel is described in U.S. Pat. No. 6,253,719. Instead of arranging next to each other the two chain wheel adjusters which are constructed in a disc-type manner, U.S. Pat. No. 6,725,817 B2 show various embodiments of a mutually nested adjuster which lies in the same plane and the first adjustment element of which can rotate a first set of cams of the concentric cam shaft, while the second adjustment element is designed to rotate a second set of cams of the concentric cam shaft. Thus, the angular rotation of one set of cams influences the accessible angular range of the other set of cams. It would be more beneficial if the sets of cams of the double cam shafts could be adjusted, as independently of one another as possible, in a further, larger adjustment range compared thereto.
The statement of object of U.S. Pat. No. 6,076,492 states that it is a problem, even in the case of simply constructed cam shaft adjusters of an axially displaceable type, to orient the cam shaft adjuster, the cylinder head, the control valve and the cam shaft in a stationary, permanent manner. Even in the case of such sufficiently known cam shaft adjusters, there is a risk of the individual components tilting relative to one another.
The described embodiments of two gas exchange valve actuating means which can be offset or adjusted relative to each other on a control shaft are included merely by way of the references thereto in the scope of the description of the present invention in order in this way to increase the readability of the description of the invention and thus to be able to emphasize more clearly the progressive aspects of the present invention.
A gas exchange valve control shaft, which is constructed from two mutually engaging, preferably coaxially arranged cam shafts surrounding the inner cam shaft, is also occasionally referred to herein as a double cam shaft. A double cam shaft is a cam shaft of dual construction. Experts frequently associate with the term “cam shaft” a single shaft on which all cams are arranged stationarily relative to one another.